How do I get particles to follow an animated path or armature?
Thank you for posting your question so clearly.

Time to get serious with particles: Select your tunnel, enter EDIT mode, switch to FACE selection filter, select all faces. Go to the MESH menu>NORMALS>Flip normals. Now all your normals should be pointing INSIDE your tunnel.

2) Switch back to OBJECT mode, now apply a SOLIDIFY MODIFIER, and make it thick enough so that when you deform your object it will deform correctly (like a real tunnel thickness)

3) Go to the dynamics tab and click COLLISION. Set friction to something like 0.2, 0.5

4) Now when you playback your animation, your (already working curve guide force) should be working and particles will not be able to scape the tunnel. Furthermore the expected behavior of the particles will react to the deformation of the tunnel.

Thank you for your consideration to vote this as the answer.

BFCT_Schiller